The invention relates to filter media, and more particularly to filter media incorporating nanofibers of diameter less than 1 μm for high performance.
Filter media with nanofibers is known in the prior art. A nanofiber filter media layer is typically provided along an upstream face surface of a bulk filter media including a layer of coarse fibers. The nanofibers extend parallel to the face of the bulk filter media layer and provide high efficiency filtering of small particles in addition to the filtering of larger particles provided by the coarse filter media. The nanofibers are provided in a thin layer laid down on a supporting substrate and/or used in conjunction with protective layers in order to attain a variety of benefits, including increased efficiency, reduced initial pressure drop, cleanability, reduced filter media thickness and/or to provide an impermeability barrier to certain fluids, such as water droplets. Prior approaches have several inherent disadvantages, including the need for a supporting substrate, a risk of delamination of the nanofiber layer from the substrate, more rapid plugging of the filter by captured contaminants, and the alignment of nanofibers parallel to the media face surface.
Also known in the prior art are filter media having cellulose coarse fibers and a mixture of glass nanofibers and microfibers in the media. These filters use stiff glass nanofibers, and use polymeric microfibers to strengthen the media. They have been used in fuel, air and hydraulic filters.
The present invention addresses and solves the above noted problems. The invention provides a fibrous filter media with nanofibers incorporated and processed into internal structure of a filter medium. The invention may be used in a variety of applications for filtering fluid, including gas such as air, exhaust, and crankcase ventilation gas, and including liquid such as oil, fuel, coolant, water, and hydraulic fluid.